Existing hall call allocation systems and methods use criteria, such as waiting time, time to destination, energy consumption, and elevator usage, with neural networks, generic algorithms, and/or fuzzy logic to find an optimum solution for assigning a new hall call to one of a group of available elevator cars. These existing systems and methods generally fall into one of two categories; Estimate Time of Arrival (“ETA”) based systems and destination dispatch based systems.
Conventional ETA based elevator systems use up and down buttons in the hallway to call the elevators. When a person wishes to call an elevator to a floor either the up or down button is pressed. The selected button is then illuminated indicating that the call has been accepted. While the call is often immediately assigned to a car, it does not need to be immediately assigned. In fact, calls are often reassigned to different cars due to changes in the traffic situation.
With destination dispatching systems the user enters his destination on a keypad or touch screen located in the hallway. Immediately a display indicates which elevator has been selected and directs the individual to proceed to that elevator and wait for the car to arrive. Reassignments or delayed assignments in such systems are not possible. Although destination dispatch systems can handle up to 50% more traffic than conventional systems, the necessity to immediately assign calls can create inefficiencies in the system.
For three or four decades elevator systems have used load weighing systems to avoid unnecessary stops. If an elevator is fully loaded, then it can not accept additional passengers. A system known in the industry as “load weighing bypass” would not permit elevators traveling down that were fully loaded to accept additional call assignments if the cars were fully loaded. This was extremely beneficial because a full elevator that makes a stop at a floor to pickup passengers that cannot enter the elevator is a false stop that degrades performance by wasting time.
Requiring calls to be assigned immediately in destination dispatching systems often means that optimal dispatching solution cannot always be utilized. When destination dispatch systems were introduced this system was used by most practitioners to assure that a person was not assigned to a car that was full regardless of car travel direction. While this was a logical decision, it could create problems if the traffic level was so intense that a dispatching solution could not be found. One must recall that destination dispatch systems must make immediate call assignments and that certain assignments are banned. In this case systems would either send a message to an I/O device that indicated that no assignment was possible such as “XX” or a textual message would be displayed such as “Unable to assign your call.” Try again later.
Both of these answers make the situation worse because passengers will repeatedly reenter their destination further overloading the system. Some high profile destination dispatch systems go into saturation daily thereby forcing people to use the stairs during peak periods.
Another example of a commonly banned assignment is associated with the direction of travel for elevator cars. For example, if a waiting passenger located on the tenth floor wants to travel to the lobby the best solution might be for an elevator traveling up to the 11th floor to pick up the waiting passenger on the way. The 10th floor passenger would be required to up travel to the 11th floor before traveling to the lobby. While this type of journey is very efficient, it is a banned assignment in virtually all destination dispatching systems.